Complementary metal oxide semiconductor (CMOS) integrated circuits increasingly make use of optical transmission structures to surpass the bandwidth limitations of copper. The use of both photonic devices in high-speed switching and transceiver devices in data communications are but a few examples that highlight the advantages of processing both optical and electrical signals within a single integrated device. For example, an integrated photonic device may include both photodetector and CMOS type devices that may be fabricated on a single silicon substrate. However, during the fabrication process, certain processes, while benefiting or being necessary for the formation and/or operation of one type of device (e.g., CMOS FET), may be detrimental to the formation and/or operation of the other type of device (e.g., Photodetector).
For example, using a single nitride to block silicide on both optical and CMOS devices results in low performance and yield. Additionally, germanium recrystallization in an encapsulant can crack the encapsulant such that the subsequent wet chemical treatments (e.g., during a silicide process) etch the germanium away. The dielectrics used for silicide protection over passive photonics can be non-uniform (i.e., too thick or too thin at locations) which causes excessive optical loss or cross talk.
It may therefore, among other things, be advantageous to maintain, within an integrated photonic device, the integrity of both photonic and non-photonic type devices during fabrication processes.